The present invention relates to improvements in dissipation of heat from socketed electronic chip carriers and the like, and, in one particular aspect, to novel and advantageous integrally-composite heat sinks and covers, for miniature socketed leadless chip carriers, which lend themselves to low-cost fabrication from sheet metal and which are constructed and disposed to make intimate broad-area heat-transfer engagements with a chip carrier and to convectively discharge heat efficiently, without making intricate socketing procedures more difficult and without imposing troublesome bulk.
Semiconductor devices, microcircuit modules and integrated circuits tend to be highly susceptible to damage from heat generated internally as efforts are made to extend their operations into higher and higher ranges of power. One common and economical expedient for expelling and forestalling the build-up of heat in such electronic items involves the attachment of small finned metal extrusions or stampings which serve to conduct heat away from their thermally-vulnerable regions and, in turn, to dissipate it by way of convective coupling with the ambient atmosphere. In some instances the items to be cooled are provided with exposed metal tabs or plates by which sheet-metal heat sinks may withdraw heat efficiently from protectively-encapsulating bodies within which the semiconductors are located (as illustrated in U.S. Pat. Nos. 3,670,215 and 4,041,524), and, in other cases, multi-pin packages of integrated circuitry are straddled by clip-on heat sinks which clasp directly against the plastic packages themselves (illustrated in U.S. Pat. Nos. 4,222,090 and 4,408,220). It has also been known to fabricate an integrated-circuitry module such that it incorporates as one original structural component a permanently-encasing metal cover shaped to promote release of heat from the circuitry within (U.S. Pat. No. 4,092,697), and radiator elements have also been glued directly onto small electronics packages to promote cooling.
The ease and convenience with which heat-sink attachments may be fitted onto packages, and the extent to which efficient heat transfer is promoted along the pathways between those attachments and the packages they serve, are highly important considerations. For example, the need to stock and handle numerous parts or to have resort to special tools and fasteners, are complications which manufacturers generally seek to avoid, for the obvious reasons, and it must also be assured that when assembly of a delicate package with its heat sink has been completed there will be intimately-connected broad-area and low-loss conductive pathways through which unwanted heat will be expelled. Such problems become intensified as the electronics packages become ever smaller, more intricate, and expensive, as in the case of modern substantially-monolithic leadless chip carrier (LCC) packages involving large scale integrated circuitry on substrates whose numerous electrical connections are in the form of tab-like contacts arrayed in rows along peripheral edges of thin square molded carriers. Those leadless chip carriers are designed for mounting within sockets which orient and hold them in secure engagements with numerous socket contacts which couple the various chip-carrier contacts with socket pins, the latter pins being the leads by which needed electrical circuit connections are completed through wiring of a printed-circuit-board to which the socket is soldered. The very small multi-pinned carrier sockets are structurally somewhat frail, and they are especially prone to injury when their carriers are being inserted or removed; accordingly, radiator-type heat-sink attachments used to protect or enhance performance of the chip circuitry can be expected to be correspondingly small and troublesome to assemble securely and without interfering with the socketing and possibly damaging the socket and carrier. In practice of the present teachings, such difficulties may be averted by way of special dual-function heat sinks which are uniquely arranged as integral portions of removable covers used to retain carriers within their sockets, each sink-cover unit not only being of low-cost construction and being conveniently dealt with as a single part but also offering the advantage that it tends to physically orient itself reliably for an essentially optimum heat-transfer relationship with a thermally-vulnerable carrier.